This invention relates to an anti-tip assembly for power wheelchairs in which a pair of drive wheels are operatively driven by one or more motors powered by an onboard battery assembly. Although the invention is particularly described with reference to a power wheelchair, it may also find application in related environments such as scooters or the like.
Power drive wheelchairs incorporating an anti-tip assembly are well known in the art. For example, commonly owned U.S. Pat. No. 5,575,348, the disclosure of which is incorporated herein by reference, is representative of an earlier generation of this product. The '348 patent shows and describes a spring dampener secured at one end to a frame and at an opposite end to an anti-tip assembly. The anti-tip assembly extends from an arm that also supports the drive motor so that the dampener acts as both a suspension for the wheelchair, as well as a portion of the anti-tip assembly that effectively resists tipping forces imposed by initial acceleration of the wheelchair.
In an effort to improve upon this commercially successful arrangement, and isolate the anti-tip assembly from the suspension during most tipping action, consideration is given to providing a separate anti-tip force resistance and using the dampener only through a latter part of a tipping action, if necessary. Because the anti-tip assembly is always connected through the suspension mechanism in the prior arrangement, there may be situations where the anti-tip mechanism of the prior arrangement lifts the drive wheels off the ground. The wheelchair could be stuck until the obstacle is overcome.
Simultaneously, it is desired to use as much of the structure of the commercially successful version as possible. This, of course, reduces inventory, and also provides for easy modification of an existing design.
Consequently, it has been considered desirable to develop a new and improved anti-tip assembly for a power wheelchair that overcomes the noted problems and achieves these various objectives.